It's not hard to see how shifting the basis of the natural law from God's Nature, self-realized in His Intellect (and therefore discernible by reason alone), to the will has resulted in the social, economic and political mess we see today throughout the world. When things are based not on some objective standard, but on our subjective opinion, might makes right, and we end up with a totalitarian society, as both Mortimer Adler and Heinrich Rommen observed.
The shift from reason to faith as the basis of the natural law has been, frankly, catastrophic. As Rommen explained,
"Stressing the irrational will, the 'heart,' the mystical faculties of the soul, and the amor (Nihil intelligitur quod non prius diligitur), and consequently exalting the will as the primary attribute in God's omnipotence, they had not a little trouble in finding a well-established basis for the strict invariability of the principles of natural law. They were also inclined to disparage the importance and range of natural reason and consequently to show supernaturalist tendencies even in their political philosophy." (Heinrich Rommen, The State in Catholic Thought. St. Louis, MO: B. Herder Book Company, 1947, 17.)
It comes as no surprise, then, that opponents of the Just Third Way (a system based on the Aristotelian/Thomist understanding of the natural law as based on God's Nature, self-realized in His Intellect and reflected in His special creation, humanity), consciously or unconsciously invariably base their attack on the presumed variability of the principles of natural law. They are motivated by love (amor), and are turned off or offended by the Just Third Way's "rigid" insistence on the principles of strict justice found in the natural law, especially the rights to life, liberty and property. Something is right not because God is so, but because they believe that God, the pope, the State, or some other authority said so. Consequently, as Rommen observed, "the essence of the natural law vanishes." (Ibid., 18.) As Rommen continued,
"If God's omnipotence was thus exalted the consequence had to be and has been a kind of nihilism in natural ethics, a transformation of the fides rationalis into an emotional faith of sentiment, the negation of natural theology and a one-sided supernaturalism. All too easily the world of politics and economics is then left to itself. This consequence tends to make the Church an obedient instrument of the state, which has the monopoly of nature, world, and power." (Ibid.)
In other words, because in this understanding of the natural law the State has the power (as Keynes asserted) to "re-edit the dictionary," the Church must bend to the State, rather than both acknowledging God and each operating within its proper sphere. The State becomes (in the words of one enthusiastic partisan of this viewpoint) "the sole intercessor available to the poor." Further, the Church shouldn't push so hard for an end to abortion or resist the HHS mandate, for that would endanger the security the State gives us and all the benefits it confers. You don't want to bite the hand that feeds you, you know.